Stripping tool for coaxial cable

ABSTRACT

The invention relates to stripping tools for coaxial cables with a corrugated outer conductor ( 9 ) and a hollow inner conductor ( 31 ). The tool comprises three main parts: a jacket cutting means ( 1 ) for removing a certain predetermined length of the jacket ( 7 ) of the cable, a guide part ( 10 ) to be placed around the end of the cable after the jacket ( 7 ) has been removed by means of said jacket cutting means ( 1 ), and a second cutting means ( 18 ) to be placed on said guide part ( 10 ) during a final preparation of the end of the cable during which the inner conductor ( 31 ), the outer conductor ( 9 ) and the dielectric material ( 32 ) between inner- and outer conductor are being cut off to appropriate lengths. The guide part ( 10 ) is provided with means ( 16, 16 ′) determining a well-defined longitudinal position of the tool on the cable relative to the pattern of valleys ( 17 ) and crests ( 33 ) of the corrugation on the outer conductor ( 9 ). Using the tool according to the invention it is thereby possible to: (a) expose a predefined length of outer conductor ( 9 ); (b) cut off the inner conductor ( 31 ) and the dielectric material ( 32 ) at a predetermined longitudinal position relative to the end of the outer conductor ( 9 ), and (c) ascertain that the outer conductor ( 9 ) is cut off substantially at a valley ( 17 ) of the corrugation.

TECHNICAL FIELD

[0001] The present invention relates to stripping tools for coaxial cables and more particularly to such tools for coaxial cables with a corrugated outer conductor and a hollow inner conductor as set forth in the preamble of claim 1.

SUMMARY OF THE INVENTION

[0002] A coaxial cable of the above mentioned kind comprises a hollow inner conductor with a longitudinal axis and coaxially with said inner conductor a tubular layer of insulating material between said inner conductor and an outer conductor which is corrugated in a non-helical manner in order to improve flexibility of the cable, said outer conductor thereby comprising a repeated axial pattern of crests and valleys, and finally provided with an outer insulating jacket.

[0003] It is an object of the present invention to provide a stripping tool for a coaxial cable with said kind of corrugated outer conductor and a hollow inner conductor, which tool is capable of performing all stripping steps required in order to prepare the cable for insertion into a coaxial connector.

[0004] More specifically said tool must be capable of providing the correct relative axial locations of the end of the inner conductor, the end of said insulating material provided between the inner and outer conductor, the end of the corrugated outer conductor and the end of the jacket. Furthermore, said correct relative axial locations must be obtained with the tool no matter at what axial location the cable is initially cut off.

[0005] These and other objects are attained with a stripping tool for said kind of coaxial cable according to the characterising clause of claim 1. Various embodiments of the tool are the subject of the dependent claims.

[0006] According to the present invention there is thus provided a stripping tool comprising the following main means:

[0007] A jacket cutting means for stripping the appropriate axial length of the jacket, thereby exposing the corresponding axial length of said outer conductor.

[0008] A guide means to be placed coaxially around the coaxial cable after said appropriate axial length of the jacket has been removed as described above, where said guide means during operation of the stripping tool guides a second cutting means and provides a well defined axial abutment surface for this means. The guide means is furthermore provided with position determining means so that it can be located at a well-defined axial position relative to said repeated pattern of crests and valleys thereby positioning said abutment surface at a well-defined axial position relative to said pattern of crests and valleys.

[0009] A second cutting means for providing the required relative axial positions of the end of the outer conductor, the corresponding end of the insulating material between the inner conductor and the outer conductor and the end of the inner conductor, said second cutting means being guided by said guide means and being provided with cutters, blades or similar means operating while the second means is being displaced axially relative to the cable along said guide means until said abutment between the second cutting means and said guide means is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention will now be described in more detail with reference to the accompanying drawings, in which

[0011]FIG. 1 a is a schematic view of a jacket cutting means according to the invention,

[0012]FIG. 1b is a schematic view of the end of a coaxial cable inserted in the jacket cutting means in an initial position prior to stripping of the jacket;

[0013]FIG. 1c is a schematic view corresponding to FIG. 1b with the coaxial cable in the final position with an appropriate length of the outer conductor exposed.

[0014]FIG. 1d is a schematic view of the jacket cutting means according to the preceding Figures provided with a handgrip.

[0015]FIG. 2a is a schematic perspective view of a guide part according to the invention,

[0016]FIG. 2b is a longitudinal sectional view of the guide part shown in FIG. 2a,

[0017]FIG. 2c is a longitudinal sectional view corresponding to FIG. 2b but with a cable prepared with the aid of the jacket cutting means inserted into the operative position in the guide part;

[0018]FIG. 2d is a longitudinal sectional view of an alternative embodiment of the guide part,

[0019]FIG. 3a is a longitudinal partly sectional view of the second cutting means according to the invention,

[0020]FIG. 3b is a schematic view of the second cutting means shown in FIG. 3a seen from the direction of the arrow A; and

[0021]FIG. 4 is a schematic partly sectional view of the finished coaxial cable.

DETAILED DESCRIPTION OF THE INVENTION

[0022] In the following, a detailed description of a preferred embodiment of the invention Is given, but it is understood that other designs of the various details in the stripping tool may be made by a person skilled in the art without departing from the scope of the invention as defined by the following claims. One such alternative embodiment, differing from the first embodiment only with respect to one particular feature is also briefly described.

[0023] The stripping tool according to the preferred embodiment of the invention consists of three main parts: a jacket cutting means 1 for exposing an appropriate length of the outer conductor of the cable as a necessary preparation for the following steps in the stripping procedure, a guide part 10 to be placed coaxially over the end of the cable prepared by the jacket cutting means 1 in the preceding step and serving as a guide- and abutment means for a second cutting means 18 for providing the correct relative longitudinal extension of exposed outer conductor, inner conductor and insulating material placed between the inner and outer conductor.

[0024]FIG. 1a shows a schematic view of the jacket cutting means 1 of the stripping tool in longitudinal cross section and seen from that end of the jacket cutting means 1 into which the end of a coaxial cable to be prepared for insertion in a connector is to be inserted. The jacket cutting means 1 essentially comprises a tubular body 2, the inner diameter of which corresponds to the outer diameter of the jacket of the coaxial cable. The tubular body 2 is open at one end 3 where the cable is to be inserted and closed at the other end by a wall 4 substantially perpendicular to the longitudinal axis through the tubular body 2. A certain length of cable can thus be inserted into the tubular body. At the inner circumferential wall of the tubular body 2 there is provided a cutting means 5 in the form of a knife blade with a cutting edge 6 facing the longitudinal axis. The cutting edge 6 starts at a longitudinal distance I from the end wall 4 of the tubular body 2, this distance 1 corresponding to the longitudinal length of cable jacket to be removed. The operation of the cutting means 1 is depicted in FIGS. 1b and 1 c. FIG. 1b shows an end of the coaxial cable 7 inserted into the tubular body 2 to an initial position where the end of the cable just touches the end of the cutting edge located the distance 1 from the end wall 4. After insertion of the cable to this point, the cable is further advanced towards the end wall 4, the tubular body 4 simultaneously being rotated about its longitudinal axis. The resultant relative movement of the cutting edge 6 and the jacket of the cable results in the jacket being cut off helically over the longitudinal distance l, thereby exposing a corresponding length of the corrugated outer conductor 9.

[0025]FIG. 2a shows a schematic view of the above mentioned guide part 10 to be placed on that end of the coaxial cable which has been prepared as described above. More specifically the guide part 10 comprises a rotationally symmetrical body composed of two sections: a tubular section 11 made of a resilient material such as hard rubber, to which section is attached a second section 12, 13, 14 made of a substantially rigid material and longitudinally cut into a number of subsections by a number of slits 15 through the wall of the second section, in this embodiment 4 subsections of equal circumferential dimensions, although other numbers of subsections could of cause also be used. By cutting up the wall of the second section longitudinally in the manner described, it is made possible for this section to undergo radial displacements except al that end of the seconds section section where it is attached to said resilient first section. As shown in FIGS. 2b and 2 c, a through bore is provided through the coaxially placed first and second sections, the diameter of this through bore substantially corresponding to the outer diameter of the jacket of the cable. It is thus possible to insert the cable into the guide part 10 from the side of the resilient first section. Furthermore, the second section is at the end hereof facing away from the first section provided with inwardly directed tongues 16.

[0026]FIG. 2c shows the guide part with a cable prepared by means of the jacket cutting means 1 inserted. Due to the radially resilient construction of the guide part, as provided by the resilient first section and the longitudinal slits 15 in the second section, it is possible to insert the end 8 of the cable to a point beyond said inwardly directed tongues 16, so that these tongues 16 thereby fit into the corrugation of the outer conductor 9 at those places 17 where the diameter of the outer conductor 9 is smallest, i.e. Into the “valleys” of the corrugation. During operation of the stripping tool the prepared cable is inserted in the guide part 10 so that said tongues 16 fit into that valley of the corrugation which is located closest to the end of the jacket 7 of the cable. In this manner a well-defined longitudinal placement of the guide part 10 on the cable is obtained, which is essential for the further operations of the stripping tool.

[0027] Referring to FIG. 2d there is shown an alternative embodiment of the position determining means, which in the embodiment described above was implemented in the form of the tongues 16 according to FIGS. 2b and 2 c. In this alternative embodiment of the position determining means, radially inwardly directed tongues 16′ are provided, where the surface of the tongues to be brought into contact with the corrugated outer conductor is provided with a recess to enable it to grip over the top of the crests 33 of the corrugation instead of fitting into the valleys as in the previously described embodiment. Otherwise the construction of the guide part does not differ from the guide part 10 according to the first embodiment.

[0028] It is understood that the construction of the guide part 10 based on the radially resilient section 11 and the split up second section 12, 13, 14, 16 is chosen in order to provide the end of the guide part 10 which is provided with said tongues 16 with sufficient radial resiliency to make it possible to pass the end of the cable through the through hole in the guide part 10 despite the presence of the radially inwardly directed tongues 16, 16′ and furthermore to obtain a fixed and reliable positioning of these tongues in the appropriate valley of the corrugation of the outer conductor. The required radial resiliency of the portion of the guide part comprising the tongues 16, 16′ could, however, also be achieved in other manners without the necessity to split up the second section of the guide part by the longitudinal slits 15. For this purpose either the end of the guide part 10 comprising the tongues 16, 16′ could be made of a suitable resilient material with the remaining longitudinal extension of the guide part, including the tubular section 11, being made of a rigid material, or the whole guide part 10 could be made of a material with sufficient radial resiliency, provided a well-defined abutment surface 13 and a well-defined longitudinal distance s (see FIG. 2c) were still obtained.

[0029] The outer surface of the second section of the guide part 10 is subdivided into three regions 12, 13, 14. In this manner, an abutment surface 13 for the second cutting means 18 mentioned initially is provided, said abutment surface 13 in this manner being located longitudinally at a well defined distance from said tongues 16, and thereby from the valley 17 in the corrugation of the outer conductor located closest to the end of the jacket (or from a corresponding crest 33 in case of the above second embodiment).

[0030] The last of the abovementioned three parts of the stripping tool according to the invention, i.e. the second cutting means 18, is shown schematicaliy in FIGS. 3a and 3 b. In FIG. 3a, a schematic longitudinal partly sectional view of the second cutting means generally indicated by 18 is shown. The second cutting means basically comprises a tubular house 20 to be placed coaxially over the previously described guide part 10, in such a manner that during operation hereof the circumferential inner surface 21 at one end of the second cutting means 18 fits on the corresponding region 12 of the guide part 10. Thus, when the guide part 10 is placed on the end of the cable as described in connection with FIGS. 2a through 2 d, the second cutting means 18 can during rotation hereof be displaced longitudinally in a well defined manner relative to the end of the cable over a longitudinal distance ultimately determined by the end face 29 during said displacement being brought into contact with the abutment surface 13 on the guide part 10. In this final position of the second cutting means 18 a well-defined longitudinal relationship between the second cutting means 18 and the various structures of the coaxial cable (i.e. the jacket 7, the outer conductor 9, the insulating layer 32 between outer and inner conductor and the hollow inner conductor 31) are thus established.

[0031] As mentioned in the disclosure of the invention the purpose of the stripping tool is to prepare the end of the cable in such a manner that the required longitudinal relationships between said structures of the cable are obtained. This is indicated in FIG. 4. Specifically the following requirements must be fulfilled: (1) The jacket 7 must be removed over the appropriate length of the outer conductor 9 as indicated by X2 in FIG. 4; (2) The end of the hollow inner conductor 31 and the insulating material 32 must be located at a distance of X1 from the end of the jacket; and (3) in order to achieve a proper fitting of a connector on the cable it is essential that the end of the outer conductor is located substantially at a “valley” of the corrugation, i.e. substantially at a part of the corrugation where this resumes the least diameter, as indicated by B in FIG. 4.

[0032] Returning to the detailed description of the second cutting means 18, said tubular house 20 comprises a first longitudinal section 21 of an inner diameter which fits the outer diameter of the corresponding section 12 on the guide part 10. In a second longitudinal section of the second cutting means 18 there is provided the cutting means 26 as such, which means 26 comprises a central longitudinal guide shaft 19 to be inserted into the end of the hollow inner conductor 31. Coaxially with the guide shaft 19 there is provided a cylindrical cutter means generally indicated by 26 in FIG. 3a comprising a first longitudinal portion containing a first cutting edge 22 and having a diameter corresponding to the smallest inner diameter of the outer conductor, so that this portion during operation can operate within the outer conductor without affecting this. When during operation the second cutting means 18 is rotated above its longitudinal axis, and hence relative to the cable, and simultaneously advanced longitudinally relative to the guide pair 10, said cutting edge 22 cuts off the inner conductor 31 and the intermediate insulating material 32 to the appropriate longitudinal distance from the end of the jacket indicated by X1 in FIG. 4. The cutter means 26 is furthermore provided with a second cutting edge 23 located at one longitudinal end of a larger diameter second portion of the cutter means 26 and at a longitudinal distance d from the first cutting edge 22. During operation of the second cutting means 18 this second cutting edge 23 cuts off the outer conductor 9 to its appropriate longitudinal length relative to the end of the jacket as indicated by X2 in FIG. 4. Thus the first two of the above-mentioned three requirements are achieved. The last of these requirements, i.e. that the end of the outer conductor be located substantially at a valley of the corrugation, is fulfilled for the following reason: As previously described when the guide part 10 is correctly positioned on the end of the cable as shown in FIG. 2c, the radial tongues 16 fits into that valley of the corrugation of the outer conductor 9 which is located closest to the end of the jacket. A well-established longitudinal relationship is thereby established between the position of that valley and the abutment surface 13 of the guide part 10. When hereafter during operation of the second cutting means 18 the end of this means 18 is brought into contact with the abutment surface 13, the second cutting edge 23 will be located at the appropriate longitudinal position relative to the abutment surface 13 and hence to said first valley of the corrugation. Provided the longitudinal dimensions of the cutter means 26 are properly chosen, corresponding to the actual longitudinal distance between the valleys of the corrugation, the outer conductor will be cut off substantially at the valley adjacent said first valley, whereby the third requirement mentioned above will be fulfilled. For the sake of clarity the second cutting means 18 according to this embodiment of the invention is shown in FIG. 3b seen from the end indicated by A in FIG. 3a, i.e. from that end into which the cable during operation of the tool is inserted. The relative radial positions of the cutting edges 22 and 23 can be seen from this Figure. LIST OF PARTS 1 Jacket cutting means 2 Tubular body of jacket cutting means 3 Open end of jacket cutting means 4 End wall of jacket cutting means 5 Cutting means of jacket cutting means 6 Cutting edge 7 Jacket 8 End of cable 9 Outer conductor 10 Guide part 11 Resilient tubular section 12 First region 13 Abutment surface 14 Second region 15 Slit 16 Tongue 17 Valley of the corrugation 18 Second cutting means 19 Guide shaft 20 Tubular house of second cutting means 21 First longitudinal section of second cutting means 22 First cutting edge 23 Second cutting edge 24 Guide track 25 Guide track 26 Cutter means 27 Drive shaft 28 Opening in second cutting means 29 End face of second cutting means 30 Hollow interior of inner conductor 31 Inner conductor 32 Insulation (dielectric) material between inner- and outer conductor 33 Crest of corrugation 

1. Stripping tool for a coaxial cable, said cable comprising a jacket, a non-helically corrugated outer conductor comprising a repeated pattern of crests and valleys and a dielectric material between said outer conductor and an inner conductor, said tool comprising means for cutting off the jacket, the outer conductor, the dielectric material between the outer conductor and inner conductor and the inner conductor at well-defined relative positions in the longitudinal direction of the cable, characterised in that a guide part (10) is provided for determining a well-defined position relative to said pattern of the corrugation of the outer conductor (9), such that said relative cut-off-positions are defined relative to this pattern.
 2. Stripping tool according to claim 1, characterised in that said guide part (10) comprises at least one position-determining member (12, 13, 14, 16), a part (16) of which member being adapted to sense the longitudinal position of said valleys of the corrugation of the outer conductor (9).
 3. Stripping tool according to claim 1, characterised in that said guide part (10) comprises at least one position determining member (12, 13, 14, 16′), a part (16′) of which member being adapted to sense the longitudinal position of said crests of the corrugation of the outer conductor (9).
 4. Stripping tool according to any of the preceding claims, characterised in that said guide part (10) comprises a radially resilient tubular body, the outer circumferential surface of which is subdivided into a first region (12) with a first diameter, a second region (14), the diameter of which can be either equal to the diameter of said first region or different herefrom, and a third region forming a radially outwardly extending abutment surface (13).
 5. Stripping tool according to claim 4, characterised in that said first (12), second (14) and third (13) regions are provided with a plurality of longitudinally extending slits (15) through the wall of said guide part (10) in order to provide said radial resiliency, and that said guide part (10) at the longitudinal end hereof adjoining said second region (14) is provided with a resilient tubular section (11)
 6. Stripping tool according to any of the preceding claims characterised in that the inner diameter of said guide part (10) corresponds to the outer diameter of the coaxial cable.
 7. Stripping tool according to any of the preceding claims, characterised in that it furthermore comprises a jacket cutting means (1) for removing the jacket (7) of the cable over a predetermined longitudinal distance (I, X2) from one end (8) of the cable, where said jacket cutting means (1) comprises a tubular body (2), the inner diameter of which corresponds to the outer diameter of the cable, where said tubular body (2) is open at one of its longitudinal ends (3) and completely or partially closed by an end wall (4) at the opposite longitudinal end, and which tubular body (2) on the inner circumferential surface is provided with a cutting means (5) for stripping the jacket (7) of the cable.
 8. Stripping tool according to any of the preceding claims, characterised in that it furthermore comprises a second cutting means (18) for cutting the outer conductor (9), the inner conductor (31) and the dielectric material (32) off at predetermined longitudinal positions relative to said pattern of the corrugated outer conductor (9), where said second cutting means (18) is formed as a tubular body comprising a first longitudinal section (21) of the inner circumferential wall of said body, the diameter of which first section (21) corresponds to the outer diameter of said first region (12) of the guide part (10), and where said first longitudinal section (21) is provided with an end face (29) such that this end face (29), during use of the stripping tool, is brought into contact with said abutment surface (13) of the guide part (10), whereby said predetermined longitudinal positions relative to the pattern of the corrugated outer conductor (9) are determined, and where said second cutting means (18) in its interior and coaxially herewith is provided with cutter means (26) comprising two cutting edges (22, 23), the longitudinal distance (d) between which corresponds to the longitudinal distance between the end (B) of the outer conductor (9) and the end of the inner conductor (31) and the insulating material (32), and where said second cutting means (18) is furthermore provided with a coaxially extending guide shaft (19) to be inserted into the hollow inner conductor (31) during use of the stripping tool.
 9. A method for stripping a coaxial cable comprising a non-helically corrugated outer conductor (9) and a hollow inner conductor (31) using the stripping tool according to any of the preceding claims, where said method comprises the following steps: (a) Stripping a predetermined length of said jacket (7) by inserting the end of the cable into the open end (3) of said jacket cutting means (1) to a point where the end of the cable is brought into contact with the cutting edge (6) of the cutting means (5) provided within the jacket cutting means (1), whereafter the jacket cutting means (1) is rotated relative to the cable, the cable being still advanced longitudinally within the jacket cutting means (1), until the end of the cable reaches the end wall (4) of the jacket cutting means (1); (b) Removal of the jacket cutting means (1) from the end of the cable; (c) Inserting the end of the cable into that open end of the guide part (10) furthest away from the position-determining tongues (16) to a longitudinal position, where said tongues (16) fit into that valley (17) of the corrugation on the outer conductor (9) which is closest to the end of the jacket (7), thereby obtaining a well-defined longitudinal position of the abutment surface (13) relative to this valley (17), (d) Inserting the first longitudinal section (21) of the second cutting means (18) over the first region (12) of the guide part (10), and when a point is reached where the inner conductor (31) and the insulating material (32) is brought into contact with the first cutting edge (22) provided on the cutter means (26) rotating said second cutting means (18) relative to the guide part (10) and still advancing said second cutting means (18) longitudinally relative to the guide part (10) until the end face (29) of the second cutting means (18) is brought into contact with the abutment surface (13) provided on the guide part (10); (e) Finally removing the second cutting means (18) and the guide part (10) from the finished cable.
 10. A method according to claim 9, where step (c) is replaced by the following step: (f) Inserting the end of the cable into that open end of the guide part (10) furthest away from the position-determining tongues (16′) to a longitudinal position where said tongues (16′) fit into that crest (33) of the corrugation on the outer conductor (9) which is closest to the end of the outer conductor (9), thereby obtaining a well-defined longitudinal position of the abutment surface (13) relative to this crest (33). 